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6359. Smiley, R., D. Wilkins, W. Uddin, S. Ott, K. Rhinhart, and S. Case. 1989. Rhizoctonia root rot of wheat and barley.. OR Agr. Expt. Sta. Special Report 840, p. 68-79..Rhizoctonia root rot is now considered the most severe root disease of barley in the PNW. It is more important than take-all and Pythium on wheat produced in drier areas (<16" precip.). Based on long-term plots at Pendleton, different management systems are unlikely to greatly influence the biological resistance of soils to Rhizoctonia. Rotational crops susceptible to Rhizoctonia include wheat, barley, peas, chickpeas, lentils, and rapeseed. The disease is less apparent on small grains after legumes than after cereals. Rhizoctonia damage is always highest on no-till systems, but yields may not suffer due to improved water relations under conservation tillage. Australian research indicates that applications of N and P fertilizers can reduce the disease. There appear to be detrimental herbicide interactions with Rhizoctonia, particularly Glean on high pH soils. Also, the use of glyphosate increased disease incidence, perhaps by signalling the pathogens to move from the dying plants to newly seeded ones. A delay of at least 2 weeks is suggested between chem kill and planting of a new crop.

6370. Smiley, R.W.. 1990. Seed treatment fungicides for wheat and barley.. Sherman Station Field Day handout, OSU, Moro, OR.Seed applied fungicides failed to improve yields of winter wheat or were inconsistent from site to site and/or year to year. The most consistent treatment for winter wheat was a combination of Apron and Vitavax 200. This mixture increased wheat yields by 3%. Fall barley yields were either unchanged or reduced, while spring barley showed the best economic response. Thus, an economic response to seed treatment is unlikely in the absence of damaging amounts of smut disease. Since control of smut depends on the combination of fungicide seed treatments and genetic resistance, which has been stable for decades, the use of untreated seed is discouraged to avoid the loss of genetic resistance by cereal cultivars.